Memory cells and methods of forming memory cells

ABSTRACT

Some embodiments include memory cells having programmable material between a pair of electrodes. The programmable material includes a material selected from the group consisting of a metal silicate with a ratio of metal to silicon within a range of from about 2 to about 6, and metal aluminate with a ratio of metal to aluminum within a range of from about 2 to about 6. Some embodiments include methods of forming memory cells. First electrode material is formed. Programmable material is formed over the first electrode material, with the programmable material including metal silicate and/or metal aluminate. Second electrode material is formed over the programmable material, and then an anneal is conducted at a temperature within a range of from about 300° C. to about 500° C. for a time of from about 1 minute to about 1 hour.

RELATED PATENT DATA

This patent resulted from a continuation of U.S. patent application Ser.No. 14/105,051, which was filed Dec. 12, 2013, and which is herebyincorporated herein by reference; which resulted from a divisional ofU.S. patent application Ser. No. 13/652,286, which was filed Oct. 15,2012, which issued as U.S. Pat. No. 8,629,421, and which is herebyincorporated herein by reference.

TECHNICAL FIELD

Memory cells and methods of forming memory cells.

BACKGROUND

Memory is one type of integrated circuitry, and is used in computersystems for storing data. Integrated memory is usually fabricated in oneor more arrays of individual memory cells. The memory cells areconfigured to retain or store memory in at least two differentselectable states. In a binary system, the states are considered aseither a “0” or a “1”. In other systems, at least some individual memorycells may be configured to store more than two levels or states ofinformation.

There is a continuing effort to produce smaller and denser integratedcircuits. The smallest and simplest memory cell will likely be comprisedof two electrically conductive electrodes having a programmable materialreceived between them. The programmable material has two or moreselectable and electrically differentiable memory states, which enablesstoring of information by an individual memory cell. The reading of thecell comprises determination of which of the memory states theprogrammable material is in, and the writing of information to the cellcomprises placing the programmable material in a predetermined memorystate. Memory devices that utilize changes in resistivity acrossprogrammable material to transition from one memory state to another aresometimes referred to as Resistive Random Access Memory (RRAM) cells.

There is a continuing goal to improve performance characteristics ofmemory cells, and a continuing goal to improve yield of memory cellsfrom fabrication processes. It would therefore be desirable to developnew memory cells, and to develop new methods of forming memory cells.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1, 3, 4, 6 and 7 are diagrammatic cross-sectional views of exampleembodiment memory cells.

FIG. 2 illustrates example operational states of an example memory cellof the type shown in FIG. 1, utilizing band gap diagrams.

FIG. 5 illustrates example operational states of an example memory cellof the type shown in FIG. 4, utilizing band gap diagrams.

FIGS. 8-11 are diagrammatic cross-sectional views of a construction atvarious process stages of an example embodiment method which may beutilized for forming memory cells.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Some embodiments include memory cells containing programmable materialwhich includes metal silicate and/or metal aluminate; and someembodiments include methods of making such memory cells. Exampleembodiments are described with reference to FIGS. 1-11.

Referring to FIG. 1, an example embodiment memory cell 10 isillustrated. Such memory cell includes a first electrode 12, a secondelectrode 14, and a programmable material 16 between the first andsecond electrodes.

The first and second electrodes may comprise any suitable compositionsor combinations of compositions. In some embodiments, the firstelectrode 12 will comprise, consist essentially of, or consist of ametal selected from the group consisting of hafnium, lanthanum,ruthenium, titanium, zirconium and mixtures thereof. In suchembodiments, the first electrode may be referred to as a reactiveelectrode, in that the metals of such electrode may be suitable forreacting with the programmable material during formation and/oroperation of the memory cell.

In some embodiments, the second electrode 14 may consist of acomposition which is non-reactive relative to the composition of theprogrammable material; and may, for example, comprise, consistessentially of, or consist of one or more of hafnium nitride, lanthanumnitride, ruthenium nitride, titanium nitride and zirconium nitride.

In some example embodiments, the first electrode 12 will comprise,consist essentially of, or consist of a metal selected from the groupconsisting of hafnium, lanthanum, ruthenium, titanium, zirconium andmixtures thereof; and the second electrode 14 will comprise, consistessentially of or consist of a metal nitride comprising the metal of thefirst electrode. For instance, in some embodiments the first electrode12 may comprise titanium while the second electrode 14 comprisestitanium nitride.

The programmable material 16 may comprise, consist essentially, orconsist of one or both of metal silicate and metal aluminate. The metalsilicate may be selected from the group consisting of hafnium silicate,lanthanum silicate, ruthenium silicate, titanium silicate, zirconiumsilicate, and mixtures thereof; and the metal aluminate may be selectedfrom the group consisting of hafnium aluminate, lanthanum aluminate,ruthenium aluminate, titanium aluminate, zirconium aluminate andmixtures thereof.

In some embodiments, the programmable material comprises a region whichincludes a composition selected from the group consisting of a metalsilicate with a ratio of metal to silicon within a range of from about 2to about 6, and a metal aluminate with a ratio of metal to aluminum witha range of from about 2 to about 6. Utilization of such compositionswithin programmable materials of RRAM cells is found to improve yield offunctional cells during a fabrication process relative to processesforming analogous cells lacking such compositions of metal silicateand/or metal aluminate, and to improve durability of the RRAM cellsrelative to cells lacking such compositions of metal silicate and/ormetal aluminate. Thus, inclusion of one or both of metal silicate with aratio of metal to silicon within a range of from about 2 to about 6, andmetal aluminate with a ratio of metal to aluminum within a range of fromabout 2 to about 6 in RRAM cells may improve yield and performance ofthe cells relative to conventional RRAM cells. In some embodiments, theutilization of metal silicate having a ratio of metal to silicon withinthe range of from about 2 to about 6 and/or metal aluminate having aratio of metal to aluminum within the range of from about 2 to about 6is found to improve low current operation of memory cells and resetcharacteristics of memory cells.

In some embodiments, the programmable material 16 may be a singlehomogeneous composition extending from directly against the firstelectrode to directly against the second electrode. In some embodiments,the programmable material 16 may comprise a concentration gradient ofmetal within one or both of metal aluminate and metal silicate. Forinstance, the programmable material may comprise a first compositionadjacent the first electrode 12, and a second composition adjacent thesecond electrode 14. The first composition may comprise the metalsilicate with a ratio of metal to silicon within a range of from about 2to about 6, and/or the metal aluminate with a ratio of metal to aluminumwithin a range of from about 2 to about 6; and the second compositionmay comprise metal silicate having a ratio of metal to silicon of atleast about 8 and/or metal aluminate having a ratio of metal to aluminumof at least about 8. In such embodiments, the first composition may bedirectly against a reactive electrode, the second composition may bedirectly against a non-reactive electrode, and the programmable materialmay have a concentration gradient of metal which extends from the firstcomposition to the second composition such that the concentration ofmetal increases across the programmable material along a direction fromthe reactive electrode to the non-reactive electrode.

In a specific example embodiment, the reactive electrode may consistessentially of titanium, the nonreactive electrode may comprise titaniumnitride, and the programmable material may consist essentially ofhafnium silicate. A region of the programmable material directly againstthe reactive electrode may have a ratio of hafnium to silicon within arange of from about 3 to about 6, a region of the programmable materialdirectly against the nonreactive electrode may have a ratio of hafniumto silicon of at least about 8, and the programmable material maycomprise a concentration gradient of hafnium which increases along adirection from the reactive electrode to the nonreactive electrode. Theregion adjacent the nonreactive electrode has a higher dielectricconstant than the region adjacent the reactive electrode (i.e., may beconsidered to have a higher ratio of hafnium oxide relative tosilicate), which may improve yield and/or device performance in someembodiments. The concentration gradient may be any suitable gradient,including, for example, a linear gradient or a stepped gradient.

Although the reactive electrode and the nonreactive electrode aredescribed to be the electrodes below and above the programmable material16, respectively, in the embodiment of FIG. 1; in other embodiments therelative positions of the reactive and nonreactive electrodes may bereversed so that the reactive electrode is above programmable material16 and the nonreactive electrode is below such programmable material.Similarly, any of the other embodiments described herein may beconstructed with an illustrated arrangement of electrodes, or with anopposite arrangement in which the electrodes (and possibly one or moreregions between the electrodes) are reversed relative to the illustratedarrangement.

FIG. 2 diagrammatically illustrates a plurality of operational states (aso-called “UNBIASED” state, “RESET” state, and “SET” state) utilizingband gap diagrams. The example embodiment comprises a first electrode 12consisting of titanium, a second electrode 14 consisting of titaniumnitride, and programmable material 16 consisting of hafnium silicatewith the ratio of hafnium to silicon being about 3:1.

The “RESET” and “SET” states have different resistivities relative toone another, and correspond to different memory states of the memorycell 10. Operation of memory cell 10 comprises programming the memorycell to place it in either the “RESET” state or the “SET” state, andlater reading the memory cell to determine which of the two states it isin. In some embodiments, operation of the memory cell may comprise amechanism in which the reactive electrode is utilized to form a thinlayer of hafnium oxide, lanthanum oxide, ruthenium oxide, titanium oxideand/or zirconium oxide in a region of the programmable material directlyadjacent such reactive electrode through reaction of metal from thereactive electrode (specifically, hafnium, lanthanum, ruthenium,titanium and/or zirconium) with oxygen of the programmable material.Such thin layer may be modulated during operation of the memory cell tooperably switch the memory cell between a low resistance state and ahigh resistance state. For instance, conductivity through theprogrammable material may be operably altered as follows. The resistancemay be decreased by pulling more oxygen into the thin layer to increasean amount of oxygen vacancies within a metal silicate matrix and/ormetal aluminate matrix, and the resistance may be increased by pullingmore oxygen from the thin layer into the metal silicate matrix and/ormetal aluminate matrix to decrease the amount of oxygen vacancies withinsuch matrices. The possible mechanism of operation of a memory cellthrough modulation of oxygen vacancies is provided to assist the readerin understanding the embodiments described herein, and is not to limitany of such embodiments except to the extent, if any, that the mechanismis explicitly recited in the claims which follow.

In some embodiments, the thin oxide layer may be provided as part of theprogrammable material, and accordingly the reactive electrode may bereplaced with any suitable conductive material. FIG. 3 shows an exampleembodiment memory cell 10 a having a programmable material 16 acomprising an oxide 20 over a composition 18. In some embodiments, theoxide 20 may comprise, consist essentially of, or consist of hafniumoxide, lanthanum oxide, ruthenium oxide, titanium oxide and/or zirconiumoxide; and the composition 18 and may include a region having one orboth of metal silicate with a ratio of metal to silicon within a rangeof from about 2 to about 6, and metal aluminate with a ratio of metal toaluminum within a range of from about 2 to about 6. In some embodiments,the oxide 20 may have a thickness of from about 10 Å to about 50 Å. Insuch embodiments, the composition 18 and may have a thickness of atleast about 50 Å, and in some embodiments may have a thickness of atleast about 100 Å.

The memory cell 10 a of FIG. 3 comprises the first and second electrodes12 and 14. In some embodiments, the composition 18 may be homogeneousbetween the electrode 12 and the oxide 20. In other embodiments, thecomposition may comprise a metal concentration gradient analogous to thevarious gradients described above with reference to FIG. 1. In yet otherembodiments, the material 18 may comprise two or more discretecompositions analogous to embodiments described below with reference toFIGS. 4-7.

Referring to FIG. 4, a memory cell 10 b is shown to comprise aprogrammable material 16 b having two regions 22 and 24, with theregions being of different compositions relative to one another.

In some embodiments, one of the regions 22 and 24 comprises acomposition having metal silicate with a ratio of metal to siliconwithin a range of from about 2 to about 6 and/or having metal aluminatewith a ratio of metal to aluminum within a range of from about 2 toabout 6. In such embodiments, the other of the regions 22 and 24 maycomprise a composition having metal silicate with a ratio of metal tosilicon of greater than 6 (and in some embodiments at least about 8)and/or having metal aluminate with a ratio of metal to aluminum ofgreater than 6 (and in some embodiments at least about 8).

The electrodes 12 and 14 may comprise any suitable materials, and insome embodiments may be a reactive electrode and a nonreactive electrodeof the types described above with reference to FIG. 1. For instance, insome embodiments electrode 12 may be a reactive electrode consisting ofone or more of hafnium, lanthanum, ruthenium, titanium and zirconium.The region 22 directly adjacent such reactive electrode may comprise afirst composition selected from the group consisting of metal silicatewith a ratio of metal to silicon within a range of from about 2 to about6, and metal aluminate with a ratio of metal to aluminum within a rangeof from about 2 to about 6. For instance, in some embodiments the region22 may comprise, consist essentially of, or consist of hafnium silicatewith a ratio of hafnium to silicon of about 3. The region 24 maycomprise a second composition selected from the group consisting of ametal silicate with a ratio of metal to silicon of at least about 6, anda metal aluminate with a ratio of metal to aluminum of at least about 6.For instance, in some embodiments the region 24 may comprise, consistessentially of, or consist of hafnium silicate with a ratio of hafniumto silicon of about 8. The electrode 14 directly against the secondregion 24 may be a nonreactive electrode, and in some embodiments maycomprise, consist essentially of, or consist of a metal nitride.

FIG. 5 diagrammatically illustrates a plurality of operational states (aso-called “UNBIASED” state, “RESET” state, and “SET” state) of the FIG.4 memory cell utilizing band gap diagrams. The example embodimentcomprises a first electrode 12 consisting of titanium, a secondelectrode 14 consisting of titanium nitride, and programmable material16 b comprising a first region 22 consisting of hafnium silicate withthe ratio of hafnium to silicon of about 3:1; and comprising a secondregion 24 consisting of hafnium silicate with the ratio of hafnium tosilicon of about 8:1.

In some embodiments, the region 22 may be considered to be a “switchingregion” where changes occur that lead to the different resistivitybetween the “RESET” state and the “SET” state. The memory cell of FIG. 5may be considered to be different than that of FIG. 2 in that the memorycell of FIG. 5 comprises a higher dielectric constant region 24 betweenthe switching region and the nonreactive electrode 14, whereas thememory cell of FIG. 2 has the switching region directly against suchnonreactive electrode. The inclusion of the higher dielectric constantregion 24 in the embodiment of FIG. 5 may enable a higher field in amemory state of the memory cell (for instance, the “SET” state) ascompared to the memory cell of FIG. 2 for a same applied voltage, due toa field distribution between the regions 22 and 24. Utilization of tworegions in the embodiment of FIG. 5 is found to improve performance andyield of memory cells relative to the embodiment of FIG. 2.

Although the embodiment of FIGS. 4 and 5 comprises two regions ofprogrammable material between the first and second electrodes 12 and 14,in other embodiments there may be more than two regions of theprogrammable material between the first and second electrodes. Forinstance, FIG. 6 shows an example embodiment memory cell 10 c havingprogrammable material 16 c with three regions 30-32 between theelectrodes 12 and 14, and FIG. 7 shows an example embodiment memory cell10 d having programmable material 16 d with four regions 40-43 betweenelectrodes 12 and 14.

In some embodiments, the regions 30-32 of FIG. 6 may be referred to asfirst, second and third regions, respectively. Each of the regions maycomprise one or both of metal silicate and metal aluminate. In someembodiments, the first and third regions 30 and 32 may comprisecompositions selected from the group consisting of metal silicate with aratio of metal to silicon within a range of from about 2 to about 6, andmetal aluminate with a ratio of metal to aluminum within a range of fromabout 2 to about 6; and the second region 31 may comprise a compositionselected from the group consisting of a metal silicate with a ratio ofmetal to silicon of at least about 6, and a metal aluminate with a ratioof metal to aluminum of at least about 6. The compositions of the firstand third regions may be identical to one another in some embodiments,and may be different from one another in other embodiments. The metalwithin regions 30-32 may comprise one or more of hafnium, lanthanum,ruthenium, titanium and zirconium, in some embodiments. In an exampleembodiment, the first and third regions 30 and 32 may both consist ofhafnium silicate with a ratio of hafnium to silicon of about 3; and thesecond region 31 may consist of hafnium silicate with a ratio of hafniumto silicon of about 8.

In some embodiments, the regions 40-43 of FIG. 7 may be referred to asfirst, second, third and fourth regions, respectively. Each of theregions may comprise one or both of metal silicate and metal aluminate.In some embodiments, the first and third regions 40 and 42 may comprisecompositions selected from the group consisting of metal silicate with aratio of metal to silicon within a range of from about 2 to about 6, andmetal aluminate with a ratio of metal to aluminum within a range of fromabout 2 to about 6; and the second and fourth regions 41 and 43 maycomprise a composition selected from the group consisting of a metalsilicate with a ratio of metal to silicon of at least about 6, and ametal aluminate with a ratio of metal to aluminum of at least about 6.The compositions of the first and third regions may be identical to oneanother in some embodiments, and may be different from one another inother embodiments. Similarly, the compositions of the second and fourthregions may be identical to one another in some embodiments, and may bedifferent from one another in other embodiments. The metal withinregions 40-43 may comprise one or more of hafnium, lanthanum, ruthenium,titanium and zirconium, in some embodiments. In an example embodiment,the first and third regions 40 and 42 may both consist of hafniumsilicate with a ratio of hafnium to silicon of about 3; and the secondand fourth regions 41 and 43 may both consist of hafnium silicate with aratio of hafnium to silicon of about 8.

The programmable materials 16 b-d of FIGS. 4, 6 and 7 may have anysuitable thicknesses, and in some embodiments may have thicknesses of atleast about 100 Å. In such embodiments, the various regions of theprogrammable materials may have any suitable thicknesses. For instance,the regions 22 and 24 of FIG. 4 may each have the same thickness as oneanother in some embodiments, or may have different thicknesses from oneanother in other embodiments. Analogously, the regions 30-32 of FIG. 6may have the same thicknesses as one another, or at least one of theregions may have a different thickness than at least one other region;and the regions 40-43 of FIG. 7 may have the same thicknesses as oneanother, or at least one of the regions may have a different thicknessthan at least one other region.

The memory cells of FIGS. 1-7 may be formed with any suitableprocessing. An example embodiment method for forming the memory cell 10of FIG. 1 is described with reference to FIGS. 8-11. Analogousprocessing may be utilized for forming other example embodiment memorycells, such as the memory cells of FIGS. 3-7.

Referring to FIG. 8, a semiconductor construction 50 is shown tocomprise conductive material 52 over a base 54. The base may comprise,consist essentially of, or consist of monocrystalline silicon, and maybe referred to as a semiconductor substrate, or as a portion of asemiconductor substrate. The terms “semiconductive substrate,”“semiconductor construction” and “semiconductor substrate” mean anyconstruction comprising semiconductive material, including, but notlimited to, bulk semiconductive materials such as a semiconductive wafer(either alone or in assemblies comprising other materials), andsemiconductive material layers (either alone or in assemblies comprisingother materials). The term “substrate” refers to any supportingstructure, including, but not limited to, the semiconductive substratesdescribed above. In some embodiments, the base may correspond to asemiconductor substrate containing one or more materials associated withintegrated circuit fabrication. In such embodiments, such materials maycorrespond to one or more of refractory metal materials, barriermaterials, diffusion materials, insulator materials, etc.

The conductive material 52 is ultimately patterned into the firstelectrode 12 of FIG. 1, and may comprise any of the compositionsdiscussed above regarding such first electrode. The conductive material52 may be formed utilizing any suitable processing, including, forexample, one or more of atomic layer deposition (ALD), chemical vapordeposition (CVD), and physical vapor deposition (PVD).

Referring to FIG. 9, programmable material 56 is formed over anddirectly against the conductive material 52. The programmable material56 may comprise any of the compositions discussed above regardingprogrammable material 16 of FIG. 1. The programmable material may beformed utilizing any suitable processing, including, for example, one ormore of ALD, CVD and PVD.

Referring to FIG. 10, a conductive material 58 is formed over theprogrammable material 56. The material 58 is ultimately patterned intothe second electrode 14 of FIG. 1, and may comprise any of thecompositions discussed above regarding such second electrode. Theconductive material 58 may be formed utilizing any suitable processing,including, for example, one or more of ALD, CVD and PVD. In someembodiments, materials 52 and 58 may be referred to as first and secondelectrode materials, respectively. The materials 52, 56 and 58 arepatterned into a memory cell 60 analogous to the memory cell 10 ofFIG. 1. The materials 52, 56 and 58 may be patterned into the memorycell configuration utilizing any suitable processing. The illustratedmemory cell may be representative of a plurality of memory cells whichare formed as part of an integrated memory array.

Referring to FIG. 11, the memory cell 60 is annealed at a temperaturewithin a range of from about 300° C. to about 500° C. for a time of fromabout 1 minute to about 1 hour, (for instance, the anneal may beconducted under conditions which maintain the materials 52, 56 and 58 ata temperature of about 400° C. for a time of about 30 minutes). Theanneal is represented by arrows 62 in FIG. 11.

The anneal of FIG. 11 is conducted after formation of electrode material58. Although the anneal is shown conducted after patterning thematerials 52, 56 and 58 into memory cell 60, in other embodiments theanneal may be conducted prior to patterning of one or more of materials52, 56 and 58 into a memory cell configuration. In some embodiments, theanneal of FIG. 11 is found to improve yield and/or performance of memorycells as compared to analogous memory cells formed with processinglacking such anneal. The performance improvement may include improvementin durability (i.e. lifetime) of memory cells in some embodiments.

The construction 50 may be kept under an inert atmosphere (for instance,N₂) during the anneal.

The anneal of FIG. 11 may be utilized for treating any of the memorycell constructions described herein. For instance, such anneal may beutilized for treating a construction of the type shown in FIG. 3 inwhich programmable material comprises a dielectric material 20 formedover a region 18 comprising one or both of metal silicate and metalaluminate. In such embodiments, the dielectric material may be formedutilizing any suitable processing, including, for example, one or bothof ALD and CVD. As another example, such anneal may be utilized fortreating constructions of the types shown in FIGS. 4, 6 and 7 in whichthe forming of the programmable material comprises forming multipledifferent compositions containing metal aluminate and/or metal silicate.

The memory cells discussed above may be incorporated into electronicsystems. Such electronic systems may be used in, for example, memorymodules, device drivers, power modules, communication modems, processormodules, and application-specific modules, and may include multilayer,multichip modules. The electronic systems may be any of a broad range ofsystems, such as, for example, clocks, televisions, cell phones,personal computers, automobiles, industrial control systems, aircraft,etc.

The particular orientation of the various embodiments in the drawings isfor illustrative purposes only, and the embodiments may be rotatedrelative to the shown orientations in some applications. The descriptionprovided herein, and the claims that follow, pertain to any structuresthat have the described relationships between various features,regardless of whether the structures are in the particular orientationof the drawings, or are rotated relative to such orientation.

The cross-sectional views of the accompanying illustrations only showfeatures within the planes of the cross-sections, and do not showmaterials behind the planes of the cross-sections in order to simplifythe drawings.

When a structure is referred to above as being “on” or “against” anotherstructure, it can be directly on the other structure or interveningstructures may also be present. In contrast, when a structure isreferred to as being “directly on” or “directly against” anotherstructure, there are no intervening structures present. When a structureis referred to as being “connected” or “coupled” to another structure,it can be directly connected or coupled to the other structure, orintervening structures may be present. In contrast, when a structure isreferred to as being “directly connected” or “directly coupled” toanother structure, there are no intervening structures present.

Some embodiments include a memory cell having a first electrode, asecond electrode, and programmable material between the first and secondelectrodes. The programmable material comprises a region containing amaterial selected from the group consisting of a metal silicate with aratio of metal to silicon within a range of from about 2 to about 6, anda metal aluminate with a ratio of metal to aluminum within a range offrom about 2 to about 6.

Some embodiments include a memory cell having a first electrode, asecond electrode and programmable material between the first and secondelectrodes. The programmable material has a first region comprising amaterial selected from the group consisting of a metal silicate with aratio of metal to silicon within a range of from about 2 to about 6, anda metal aluminate with a ratio of metal to aluminum within a range offrom about 2 to about 6. The programmable material has a second regioncomprising a material selected from the group consisting of a metalsilicate with a ratio of metal to silicon of greater than 6, and a metalaluminate with a ratio of metal to aluminum of greater than 6.

Some embodiments include a memory cell having a first electrode, asecond electrode and programmable material between the first and secondelectrodes. The first electrode consists of metal selected from thegroup consisting of hafnium, lanthanum, ruthenium, titanium, zirconium,and mixtures thereof. The programmable material has a first regiondirectly against the first electrode and comprising a first compositionselected from the group consisting of a metal silicate with a ratio ofmetal to silicon within a range of from about 2 to about 6, and a metalaluminate with a ratio of metal to aluminum within a range of from about2 to about 6. The programmable material has a second region directlyagainst the second electrode and comprising a second compositionselected from the group consisting of a metal silicate with a ratio ofmetal to silicon of at least about 6, and a metal aluminate with a ratioof metal to aluminum of at least about 6.

Some embodiments include a method of forming a memory cell. Firstelectrode material is formed over a base, and programmable material isformed over the first electrode material. The programmable materialincludes a region comprising a composition selected from the groupconsisting of a metal silicate with a ratio of metal to silicon within arange of from about 2 to about 6, and a metal aluminate with a ratio ofmetal to aluminum within a range of from about 2 to about 6. Secondelectrode material is formed over the programmable material. After thesecond electrode material is formed, the memory cell is annealed at atemperature within a range of from about 300° C. to about 500° C. for atime of from about 1 minute to about 1 hour.

In compliance with the statute, the subject matter disclosed herein hasbeen described in language more or less specific as to structural andmethodical features. It is to be understood, however, that the claimsare not limited to the specific features shown and described, since themeans herein disclosed comprise example embodiments. The claims are thusto be afforded full scope as literally worded, and to be appropriatelyinterpreted in accordance with the doctrine of equivalents.

We claim:
 1. A method of forming a memory cell, comprising: forming first electrode material over a base; forming programmable material over the first electrode material; the programmable material comprising a region comprising a composition selected from the group consisting of a metal silicate with a ratio of metal to silicon within a range of from about 2 to about 6, and a metal aluminate with a ratio of metal to aluminum within a range of from about 2 to about 6; and forming second electrode material over the programmable material and subsequently annealing the programmable material.
 2. The method of claim 1 wherein the forming of the programmable material further comprises forming a dielectric material over the region; the dielectric material having a thickness within a range of from about 10 Å to about 50 Å, and comprising one or more of hafnium oxide, lanthanum oxide, ruthenium oxide, titanium oxide and zirconium oxide.
 3. The method of claim 2 wherein the dielectric material comprises one or both of hafnium oxide and zirconium oxide.
 4. The method of claim 1 wherein the region is a first region; and further comprising forming an additional region of the programmable material, with said additional region comprising a composition selected from the group consisting of a metal silicate with a ratio of metal to silicon greater than 6, and a metal aluminate with a ratio of metal to aluminum greater than
 6. 5. The method of claim 4 wherein the additional region is formed before the first region.
 6. The method of claim 4 wherein the additional region is formed after the first region.
 7. The method of claim 1 wherein both electrode materials are directly against the programmable material; wherein one of the electrode materials is of a composition that chemically interacts with the programmable material, wherein the other of the electrode materials is of a composition that does not chemically interact with the programmable material; and wherein the programmable material comprises a higher concentration of metal adjacent said other of the electrode materials than adjacent said one of the electrode materials.
 8. The method of claim 7 wherein said one of the electrode materials consists of metal selected from the group consisting of hafnium, lanthanum, ruthenium, titanium, zirconium, and mixtures thereof.
 9. A memory cell containing programmable material which comprises: a first region which includes a material selected from the group consisting of a metal silicate with a ratio of metal to silicon within a range of from about 2 to about 6, and a metal aluminate with a ratio of metal to aluminum within a range of from about 2 to about 6; and a second region comprising a material selected from the group consisting of a metal silicate with a ratio of metal to silicon of greater than 6, and a metal aluminate with a ratio of metal to aluminum of greater than
 6. 10. The memory cell of claim 9 wherein the second region comprises a material selected from the group consisting of a metal silicate with a ratio of metal to silicon of at least about 8, and a metal aluminate with a ratio of metal to aluminum of at least about
 8. 11. The memory cell of claim 9 wherein the programmable material comprises a third region; and wherein the third region comprises a material selected from the group consisting of a metal silicate with a ratio of metal to silicon within a range of from about 2 to about 6, and a metal aluminate with a ratio of metal to aluminum within a range of from about 2 to about
 6. 12. The memory cell of claim 11 wherein the second region is between the first region and the third region.
 13. The memory cell of claim 11 wherein the programmable material comprises a fourth region; and wherein the fourth region comprises a material selected from the group consisting of a metal silicate with a ratio of metal to silicon of greater than 6, and a metal aluminate with a ratio of metal to aluminum of greater than
 6. 